Title: Inflammatory Resolution and Vascular Restoration in Diabetic Retinopathy ABSTRACT Diabetic retinopathy (DR) remains a leading cause of blindness in the United States. Recent clinical trials reveal targeting vascular endothelial growth factor (anti-VEGF) for diabetic macular edema (DME) reduces edema and improves vision in about half of treated patients. However, alternative treatment is needed for the large number of patients who do not respond to anti-VEGF therapies. The current application presents a novel approach to understand disease pathology and apply preclinical testing to a potential treatment for DR. Our novel hypothesis is that diabetes impairs the retina's reparative mechanisms, and that this contributes to the accumulation of unrepaired damage in the diabetic retina. In this proposal we will explore how diabetes impairs the retina's ability to resolve inflammation and to restore the inner blood-retinal barrier (iBRB) after injury. This is analogous to the deficiency in skin wound healing that results in non-healing diabetic foot ulcers. Although recent studies have begun to shed light on formation of the iBRB during eye development, little is known about the mechanisms governing maintenance and restoration of the iBRB in the adult. This represents a major knowledge gap that is highly relevant to DR prevention and treatment since restoring the iBRB is precisely what we strive to achieve for treatment of DME. The transformative approach is to use a retinal injury, in much the same way that skin laceration is used to study the effects of diabetes on wound healing, with the goal of overcoming diabetes induced inhibition of repair and promoting retinal restoration. These studies therefore utilize the mouse retinal ischemia-reperfusion (IR) injury model to examine the effects of diabetes on mechanisms governing restoration of the iBRB. IR injury mimics several characteristics of DR pathology, including: inner retina neuron loss, microglial activation, leukostasis, barrier tight junction disorganization, and vascular permeability. We believe that IR is the optimal choice of retinal injury to study the effects of diabetes on reparative mechanisms because IR is the only retinal injury model that includes self-resolving inflammation and extended vascular permeability followed by restoration of the iBRB. Preliminary data shows that restoration of the iBRB after IR injury normally occurs over 2-3 weeks but is defective in diabetic mice, and this coincides with amplification of innate immune responses. To determine how diabetes impedes inflammatory resolution and retinal vascular restoration, we will complete three Specific Aims: 1: Understand the process of vascular barrier restoration. 2. Identify the mechanism by which diabetes impedes restoration of the iBRB. 3. Target atypical PKC-mediated inflammation to promote barrier restoration. The research efforts represent a close collaboration between the Abcouwer and Antonetti laboratories expert in retinal inflammation and the blood retinal barrier, respectively. The research is expected to provide novel insight into mechanisms of iBRB restoration and provide additional therapeutic options to promote this process in patients.